The invention relates to a frame for forming coverings for ground openings constructed for receiving one or more juxtaposed covers or gratings and assembled from several frame parts provided with a frame base and a frame wall and which are interconnected by a screw coupling for forming the frame.
Coverings, in which one or more covers or gratings are inserted in a frame are known in numerous different forms. Such coverings are used for covering ground openings of all types, e.g., for covering manholes and openings in the floors and stories of buildings, such as warehouses, workshop halls and the like, so that it is possible to walk or drive over them and also easily open them.
In known constructions (Swiss Patent 313,512 and British Patent 2,134,572), the frame comprises several frame parts. These frame parts are butted together and screwed together at the abutment points, so that they then form a closed frame. The frame is then laid flush in the ground. For this purpose, the frame parts have a frame wall, whose upper edge is flush with the ground and a frame base, which serves as a support for a cover or a grating, which is used for covering the ground opening.
The use of individual frame parts makes it possible not only to form a frame for a single cover or grating, but also frames for receiving two or more covers or gratings enabling the covering of larger ground openings.
However, it is disadvantageous in the known constructions that the expenditure for producing such coverings is relatively high, because the abutment points of the frame parts and the covers and gratings must be at least partly mechanically worked. This is due to the tolerances of the frame parts, covers and gratings produced almost exclusively in a casting process. These tolerances do not permit a completely satisfactory assembly, particularly when the frame parts are screwed together.